Reducing unnecessary blood smear examinations: can Sysmex blood cell analysers help?
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Background: The microscopic assessment of a peripheral blood smear is an essential diagnostic tool. Many haematology laboratories currently assess smears microscopically for every full blood count request, many of which may however be assessed unnecessarily – an important consideration in resource-constrained settings. Modern blood cell analysers are increasing in sophistication and can flag abnormal specimens that may require microscopy. Objectives: To evaluate the flagging efficiency of the Sysmex haematology analysers and to determine whether this potentially labour-saving technology could assist in safely reducing the number of unnecessary microscopic blood smear assessments. Methods: A total of 427 full blood count specimens collected consecutively over a 24-hour period at NHLS Pelonomi and NHLS Kimberley, were evaluated microscopically and compared with the instruments' abilities to flag potential morphological abnormalities. Results: The Sysmex blood cell analysers flagged 63.7% of specimens as "positive" and 36.3% as "negative". After microscopy, false positive flags were found to constitute 18.5% and false negative flags 5.4% of the total number of smears reviewed, giving a total of 23.9% incorrect assessments. No false negative flag was clinically critical. Conclusion: False negative results occurring with the Sysmex instruments' flagging systems in our settings are relevant, although not critical. The potential time and monetary savings of a flagging-based smear review policy may weigh heavier than occasional false negatives. In the African milieu, where laboratories are faced with the challenges posed by staff- and other shortages, relying on instrumentation flagging to guide smear review policy should be considered.